Synthesis and Structure of Hydroxyl Acids of General Structure 7,7-Alkenyl/alkynyl-5-hydroxymethyl-6-oxabicyclo[3.2.1]octane- 1-carboxylic Acid

The open-ended hollow tubular structure formed by inclusion of water molecules in the packing of the hydroxyl acid <b>1</b> (R<sub>1</sub> = CH<sub>2</sub>OH, R<sub>2</sub> = ethyl groups) led to the synthesis and structural study of their unsaturated analogues. In this article we report on a general and practical large-scale synthesis of hydroxyl acids that possess alkenyl and alkynyl appendages. Substitution of the ethyl groups in <b>1</b> with unsaturated two-carbon appendages has a different effect on the molecular structure and on the hydrogen-bonding pattern. No variation has been induced by substitution of only one ethyl group with a vinyl one, although the substitution of both ethyl groups with vinyl or acetylene appendages has the greatest effect on the molecular structure and results in different hydrogen-bonding motifs.